It is well known in the prior art to provide a drainage device which serves to maintain a required degree of negativity within the pleural cavity of a patient and to remove fluids from within the pleural cavity so that the lungs of the patient can fully expand. U.S. Pat. No. 3,363,626 issued Jan. 16, 1968 discloses the first unitary system for achieving these results. This device provides a collection chamber, an underwater seal chamber which prevents atmospheric air from entering the patient's pleural cavity and a pressure manometer chamber which maintains the degree of suction at the proper level within the collection chamber and patient's pleural cavity. During normal operation of the drainage device of the type disclosed in the above-mentioned patent, air from the patient's pleural cavity bubbles through the underwater seal chamber and out through the device through the suction outlet. The physician may observe the passage of bubbles through the underwater seal chamber but obviously this is only possible when the physician is with the patient. Thus, there is a need for providing a drainage device which will incorporate diagnostic systems which will keep hospital personnel aware of the functioning of the drainage device and the condition of the patient.
In U.S. Pat. No. 4,617,020 issued Oct. 14, 1986 there is disclosed an air leak detector and counter for a drainage device wherein bubbles are detected electronically as the bubbles pass through the underwater seal chamber and an output circuit is provided which is responsive to the signals and both counts the number of bubbles passing through the underwater seal and resets a timer at zero each time a bubble passes through the device so that the physician can, by looking at the timer, determine the time elapsed since the last bubble went through the seal chamber. It is important for the physician to know how long a time period has elapsed since a bubble went through the bubble chamber so that the physician can determine when the patient is sufficiently healed that the drainage device may be removed from connection with the pleural cavity of the patient. If, for example, the physician decides that a three hour time period without passage of a bubble is sufficient to release a patient from the hospital, the drainage device may be disconnected from the patient when the timer shows that a three hour time period elapsed since a bubble passed through the drainage device. However, it is also desirable to provide a mechanism which will ensure that the drainage device is operating properly when it is initially connected to the patient's pleural cavity. It is most important that the physician is made immediately aware of any malfunction of the drainage device in order to prevent collapse of the patient's lungs which could, of course, prove fatal. The presently disclosed invention achieves all of the foregoing objectives.